Plasma addressed liquid crystal display with etched glass spacers

ABSTRACT

A flat display device, preferably of the PALC type, in which the plasma channels are formed by etching laterally-spaced slots in a spacer plate, attaching a thin dielectric sheet over the etched spacer plate, and bonding the etched spacer plate to a transparent substrate such that each channel is formed by the portion of the substrate between flanking walls formed by the etched slots in the spacer plate, adjacent flanking walls in the spacer plate, and the overlying portion of the thin dielectric sheet. By positioning the flanking walls between channel electrode pairs, thus providing glass-to-glass interfaces, anodic bonding can be employed to assemble the three channel elements. Etching can be simplified by pre-attaching the unetched channel plate to the substrate or thin dielectric cover sheet with an intervening etch stop, and etching in situ using the etch stop to prevent etching of the substrate or thin dielectric cover sheet. In a modification, the thin dielectric cover sheet as a separate element is substituted by depositing a continuous layer or multi-layers including an etch stop on the unetched spacer plate so that, following the etching, the deposited layer or multi-layer remains as the thin channel cover.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional of application Ser. No. 08/588,799, filed Jan. 19,1996 Now U.S. Pat. No. 5,804,920.

RELATED APPLICATIONS

1) application, Ser. No. 08/384,090, filed Feb. 6, 1995 (5604-0381).

2) application, Ser. No. 08/413,052, filed Mar. 29, 1995 (5604-0382).

3) application, Ser. No. 08/573,742, filed Dec. 18, 1995 (5604-0394).

4) application, Ser. No. 08/588,800, filed Jan. 19, 1991 (5604-0383).

BACKGROUND OF INVENTION

This invention relates to plasma channels, to display devices comprisingplasma channels, and to plasma-addressed liquid crystal display panelscommonly referred to as “PALC” display devices using such channels. PALCdevices comprise, typically, a sandwich of: a first substrate havingdeposited on it parallel transparent column electrodes, commonlyreferred to as “ITO” columns or electrodes since indium-tin oxides aretypically used, on which is deposited a color filter layer; a secondsubstrate comprising parallel sealed plasma channels corresponding torows of the display crossing all of the ITO columns and each of which isfilled with a low pressure ionizable gas, such as helium, neon and/orargon, and containing spaced cathode and anode electrodes along thechannel for ionizing the gas to create a plasma, which channels areclosed off by a thin transparent dielectric sheet; and a liquid crystal(LC) material located between the substrates. The structure behaves likean active matrix liquid crystal display in which the thin filmtransistor switches at each pixel are replaced by a plasma channelacting as a row switch and capable of selectively addressing a row of LCpixel elements. In operation, successive lines of data signalsrepresenting an image to be displayed are sampled at column positionsand the sampled data voltages are respectively applied to the ITOcolumns. All but one of the row plasma channels are in the de-ionized ornon-conducting state. The plasma of the one ionized selected channel isconducting and, in effect, establishes a reference potential on theadjacent side of a row of pixels of the LC layer, causing each LC pixelto charge up to the applied column potential of the data signal. Theionized channel is turned off, isolating the LC pixel charge and storingthe data voltage for a frame period. When the next row of data appearson the ITO columns, only the succeeding plasma channel row is ionized tostore the data voltages in the succeeding row of LC pixels, and so on.As is well known, the attenuation of the backlight or incident light toeach LC pixel is a function of the stored voltage across the pixel. Amore detailed description is unnecessary because the construction,fabrication, and operation of such PALC devices have been described indetail in the following U.S. patents and publication, the contents ofwhich are hereby incorporated by reference: 4,896,149; 5,077,553;5,272,472; 5,276,384; and Buzak et al., “A 16-Inch Full Color PlasmaAddressed Liquid Crystal Display”, Digest of Tech. Papers, 1993 SID Int.Symp., Soc. for Info. Displ. pp. 883-886.

A partial perspective view of the PALC display described in the 1993 SIDDigest is shown in FIG. 2. The method described in the referencedpublication for making the plasma channels is to chemically etch a flatglass substrate to form parallel semi-cylindrically shaped recessesdefined by spaced ridges or mesas and to bond on top of the mesas a thindielectric cover sheet having a thickness in the range of about 30-50μm.

The above construction and its fabrication encounters certain problems.Since the channel electrodes must be patterned on the sloping sidewallof the channel, the dimensions and placement of the electrodes cannot beaccurately controlled. Moreover, since slight variations in processingconditions can alter the etch rate, the channel etching process isdifficult to control; hence the depth of the channel, which is dependenton control of the etching process, is difficult to control.

European Patent 0 500 084 A2 describes the formation of channels bypatterning of electrodes on a flat substrate, providing spacers on theflat substrate, and placing the thin glass sheet on top of the spacers.The discharge space thus extends continuously across the electrodes.However, the continuous discharge space will lead between channels tocrosstalk which is difficult to avoid. Moreover, the spacers have to beformed on the flat substrate by deposition and/or etching processes,such as screen printing. Since the spacers have to be as thick as therequired channel depth (˜100 microns or more) the fabrication of thespacers adds complexity to the process.

European Patents 0 500 085 A2 and 0554 851 A1 describe the formation ofchannels by screen printing partition walls. However, this is also adifficult process, which may require multiple coats to obtain therequired wall height.

SUMMARY OF INVENTION

An object of the invention is an improved channel plate.

A further object of the invention is an improved plasma-addresseddisplay device.

Another object of the invention is an improved method for fabricatingthe plasma channels of a PALC display device.

In accordance with a first aspect of the invention, a channel platecomprises a dielectric substrate and a thin dielectric sheetlike memberarranged over and spaced from the substrate by a plurality of laterallyspaced, channel-defining spacer members each formed as part of adielectric sheet patterned by through-holes, which latter sheet isherein referred to as the spacer sheet or plate. The holes areconfigured to form the desired channel configurations, typicallyelongated parallel channels, which preferably are straight but whichalso may be curved while still maintaining a substantially parallelrelationship. The height of the spacer sheet above the substratedetermines the height of the channels, which are each formed by theportion of the substrate surface extending between adjacent flankingspacers, the flanking spacers themselves forming the channel walls, andthe overlying portion of the thin dielectric sheet-like member. Spacedelectrodes are provided in each channel as well as a plasma-formingatmosphere. The channels are formed when the three sheet-likemembers—the substrate, the spacer plate, and the thin dielectricsheet—are assembled and bonded together. By locating the spacer wallsbetween the electrodes, so that the walls contact directly the substratesurface or an ion-forming layer on the substrate, the three sheet-likemembers can be attached by anodic bonding, a well-known process usingheat and an electric field to cause mobile ions in the contactingmaterials to migrate to the sheet interfaces and bond them together.

In accordance with a second aspect of the invention, an etch stop layeris provided on the facing surface of the substrate or on the facingsurface of the thin dielectric sheet-like member, the spacer plateattached to the member containing the etch stop layer, and the etchingconducted in situ using an etch mask on the exposed surface of thespacer plate, the etchant penetration into the sheet containing the etchstop automatically stopping when the etch stop layer is reached. Thissimplifies not only the etching step but also simplifies handling ofthese fragile sheet-like members.

In accordance with a third aspect of the invention, the thin dielectricsheet-like member, as a separate element, can be avoided by depositingon the surface of the spacer plate a continuous layer or layerscomprising an etch stop material to a thickness sufficient for thedeposited layer to span without breaking or other damage thethrough-holes etched in the spacer plate and to seal off theplasma-forming atmosphere subsequently introduced into the channels. Thedeposited layer or layers thereby forms the required thin dielectriccover sheet for the channels.

In accordance with a first preferred embodiment of the invention, thesubstrate is of glass, the thin dielectric sheet is of glass, and thespacer sheet is a glass plate, with the through-holes formed by chemicalor plasma etching or by mechanical means such as sandblasting. The threeglass members may be bonded together using fused glass frit as describedin several of the cited patents and publications, or by anodic bondingas described in the first related patent application identified above.

In accordance with another preferred embodiment of the invention, thechannel plate is part of a PALC display device, and the combination ofthe substrate, patterned spacer plate and the overlying thin dielectricsheet-like member, together with the electrodes, constitutes the plasmachannels or channel plate of the PALC display device.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference should be had to the accompanying drawings and descriptivematter in which there are illustrated and described the preferredembodiments of the invention, like reference numerals or letterssignifying the same or similar components.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic block diagram of a conventional flat panel displaysystem;

FIG. 2 is a perspective view of part of a conventional PALC displaydevice;

FIG. 3 is a perspective view of a part of one form of a channel plateaccording to the invention for use in a PALC color display, and FIG. 4is a top view of the spacer plate used in that channel plate;

FIG. 5 is an exploded side view of the channel plate of FIG. 3;

FIGS. 6 and 7 are exploded views illustrating two channel plate variantsusing etch stops in different ways in accordance with the invention;

FIG. 8 is an exploded view of still further variants in accordance withthe invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a flat panel display system 10, which represents a typicalPALC display device and the operating electronic circuitry. Withreference to FIG. 1, the flat panel display system comprises a displaypanel 12 having a display surface 14 that contains a pattern formed by arectangular planar array of nominally identical data storage or displayelements 16 mutually spaced apart by predetermined distances in thevertical and horizontal directions. Each display element 16 in the arrayrepresents the overlapping portions of thin, narrow electrodes 18arranged in vertical columns and elongate, narrow channels 20 arrangedin horizontal rows. (The electrodes 18 are hereinafter referred to fromtime to time as “column electrodes”). The display elements 16 in each ofthe rows of channels 20 represent one line of data.

The widths of column electrodes 18 and channels 20 determine thedimensions of display elements 16, which are typically of rectangularshape. Column electrodes 18 are deposited on a major surface of a firstelectrically nonconductive, optically transparent substrate 34 (FIG. 2),and the channel rows are usually built into a second transparentsubstrate 36. Skilled persons will appreciate that certain systems, suchas a reflective display of either the direct view or projection type,would require that only one substrate be optically transparent.

Column electrodes 18 receive data drive signals of the analog voltagetype developed on parallel output conductors 22′ by different ones ofoutput amplifiers 23 (FIG. 2) of a data driver or drive circuit 24, andchannels 20 receive data strobe signals of the voltage pulse typedeveloped on parallel output conductors 26′ by different ones of outputamplifiers 21 (FIG. 2) of a data strobe or strobe means or strobecircuit 28. Each of the channels 20 includes a reference electrode 30(FIG. 2) to which a reference potential, such as ground, common to eachchannel 20 and data strobe 28 is applied.

To synthesize an image on the entire area of display surface 14, displaysystem 10 employs a scan control circuit 32 that coordinates thefunctions of data driver 24 and data strobe 28 so that all columns ofdisplay elements 16 of display panel 12 are addressed row by row in rowscan fashion as had been described. Display panel 12 may employelectro-optic materials of different types. For example, if it uses suchmaterial that changes the polarization state of incident light rays,display panel 12 is positioned between a pair of light polarizingfilters, which cooperate with display panel 12 to change the luminanceof light propagating through them. The use of a scattering liquidcrystal cell as the electro-optic material would not require the use ofpolarizing filters, however. All such materials or layers of materialswhich attenuate transmitted or reflected light in response to thevoltage across it are referred to herein as electro-optic materials. AsLC materials are presently the most common example, the detaileddescription will refer to LC materials but it will be understood thatthe invention is not limited thereto. A color filter (not shown) may bepositioned within display panel 12 to develop multi-colored images ofcontrollable color intensity. For a projection display, color can alsobe achieved by using three separate monochrome panels 12, each of whichcontrols one primary color.

FIG. 2 illustrates the PALC version of such a flat display panel usingLC material. Only 3 of the column electrodes 18 are shown. The rowelectrodes 20 are constituted by a plurality of parallel elongatedsealed channels underlying (in FIG. 2) a layer 42 of the LC material.Each of the channels 20 is filled with an ionizable gas 44, closed offwith a thin dielectric sheet 45 typically of glass, and contains on aninterior channel surface first and second spaced elongated electrodes30, 31 which extend the full length of each channel. The first electrode30 is grounded and is commonly called the anode. The second electrode 31is called the cathode, because to it will be supplied relative to theanode electrode a negative strobe pulse sufficient to cause electrons tobe emitted from the cathode 31 to ionize the gas. As explained above,each channel 20, in turn, has its gas ionized with a strobe pulse toform a plasma and a grounded line connection to a row of pixels in theLC layer 42 above. When the strobe pulse terminates, and afterdeionization has occurred, the next channel is strobed and turned on.Since the column electrodes 18 each cross a whole column of pixels,typically only one plasma row connection at a time is allowed on toavoid crosstalk.

Fabrication of a PALC device is typically done as described in the 1993SID digest paper by providing first and second substrates 34, 36 withthe first substrate 34 comprising a glass panel on which isvapor-deposited the ITO column electrodes 18, followed by color filterprocessing over the ITO electrodes to produce the RGB stripes (notshown), followed by the black surround processing and liquid crystalalignment processing. The second substrate 36, also a glass panel, ismasked and etched to form the channels 20, following which the plasmaelectrode material is deposited and masked and etched to form thecathode 31 and anode 30 electrodes. A thin dielectric glass microsheet45 is then sealed across the peripheral edges of the device to form withthe ridges 50 the channels 20, which are then exhausted, back-filledwith a low-pressure ionizable gas such as helium and/or neon andoptionally with a small percentage of other noble gases and sealed off.LC alignment of the exposed surface of the microsheet 45 is then carriedout. The two assembled substrates are then assembled into a panel withthe two LC alignment surfaces spaced apart and facing, the LC material42 introduced into the space, and electrical connections made to thecolumn electrodes 18 and plasma electrodes 30, 31.

FIG. 3 is a perspective view of part of one form of channel plate 52 inaccordance with the invention for one form of liquid crystal displaypanel in accordance with the invention. A thick flat glass bottom plate36 forms a substantially transparent dielectric substrate for the plasmachannels 20. Over the bottom plate 36 is deposited spaced electrodelayer portions 30, 31.

In accordance with the invention, the channels walls are formed in atransparent dielectric sheet 50 substantially equal in thickness to therequired channel depth. The dielectric sheet 50 is preferably of anetchable material, such as glass. This is accomplished with glass byetching through-holes 52 in the glass using conventional masking andetching processes.

Two preferred ways for etching the glass to make the hole walls as closeto the vertical as possible are described in FIGS. 6 and 7 of the fourthreferenced related application, whose contents are incorporated herein.In brief, this can be done as one-sided etching with an etch mask on onesurface of the spacer plate and with relatively small openings in theetch mask and etching holes whose lateral dimensions are at least fivetimes larger than the mask opening and the depth of the hole, in thiscase the thickness of the sheet 50. Using an isotropic etchant duringthe etching process, as the etching progresses, the sidewalls becomesteeper. The larger the lateral dimensions of the etched hole relativeto the thickness of the glass sheet 50, the steeper the sidewalls. As anexample, not meant to be limiting, for a glass sheet 50 of about 100 μmthick, to etch holes that are 500 μm wide, the mask hole is preferably100 μm wide. For a panel with straight channels as illustrated in FIG.2, the holes 52 would be elongated slots extending nearly the fulllength of the plate 50, but would terminate at opposite sides in anannular glass border region 53 so that the plate 50 remains as anintegral element except for the holes 52 in the form of parallel slotsspaced apart by spacer walls 58.

Alternatively, the spacer walls can be made even more vertical bycarrying out the etching from both sides of the plate 50. In this case,etch masks are required on both sides of the plate except where theholes are to be formed, and the mask holes overlie one another.

The thickness of the channel sidewalls 58 thus produced, it will beappreciated, represents the height of the channels 20 and constitute thespacers that space the thin dielectric sheet 45 that closes off thechannels from the substrate 36, and thus the reference to the aperturedplate 50 as the spacer plate. The etching can be by conventionalchemical etchants or by conventional plasma etching. Alternatively, amechanical erosion process can be substituted, such as sandblasting.This may be less costly and could also be used for materials for thespacer plate 50 that are more difficult to etch.

The channel electrodes 30, 31 are separately deposited and patterned onthe substrate 36 as described in the referenced papers and patents,after which the thin glass sheet 45 is attached over the aperturedspacer plate 50, and the latter then aligned and attached to thesubstrate 36 containing the electrodes. As shown, by proper positioningof the electrodes and the spacer plate walls 58 so as to lie betweenadjacent electrode pairs 31, 30, then the glass spacer walls 58 woulddirectly contact the glass substrate 36 surface. Adjacent channels 20would each contain its own electrode pair. Because the glass walls aredirectly in contact with the glass substrate surface, or ion-containinglayers on the surfaces, all three sheets 36, 50, 45 can be anodicallybonded to each other thereby avoiding the frit sealing process. It willalso be appreciated that the electrodes 30, 31 can be deposited on thesubstrate 36 after the spacer plate 50 has been bonded to the substrate36 instead of before as described above.

The walls 58 are shown with a slightly tapered shape, which would followif the single-sided etching technique were used, as the glass surfacescloser to the mask hole would etch more than the more remote glassportions. If the double-sided etching process were used, then a doubletaper would result.

While the attaching of the thin dielectric sheet 45 to the spacer plate50, and the attaching of the spacer plate 50 to the substrate 36 canalso be carried out using fused glass frit at the periphery of thestructure, anodic bonding preferably is used. Anodic bonding as such isa well known process for bonding two flat surfaces of ion-containingmaterials, such as glass. In a typical process, the glass sheets areplaced against each other and an electric field applied across themwhile heating them to some intermediate elevated temperature whichallows glass ions to become mobile. The ions migrate to the interfacebetween the two sheets and pulls them together. The resultant force, inthe presence of heat, leads to the formation of a permanent bond betweenthe two sheets. Typical temperatures are much lower than the softeningtemperature of the glass.

The resultant assembled channel plate structure 52 is shown in FIG. 3.The remainder of the PALC panel can be fabricated in the usual way byfilling and sealing the plasma panel and then forming the LC part of thepanel on top of the thin glass sheet 45 as shown in FIG. 5 in anexploded view. The upper plate 34 may have deposited spacer members 60which are aligned with the spacer walls 58 and act to space apart theupper structure 34 with its ITO electrodes 18 from the glass sheet 45 toprovide a confined space for the LC material.

Two variants of the invention use an etch stop layer to controlpenetration of the etchant into any etchable material attached to thespacer plate while the etching process is carried out. In the variantillustrated in FIG. 6, an etch stop layer 70 is deposited on thesubstrate 36. The etch stop layer 70 may be any thin ion-containingdielectric layer that will etch much slower, preferably at least fivetimes slower, than the material of the spacer plate 50. Suitablematerials are, for example, silicon nitride, or a thin amorphous siliconlayer, to a thickness of, for example, 1 μm. Both if these materialsetch much slower in an hydroborofluoric etchant for the glass spacerplate 50. Next, the unetched spacer plate 50 can be attached as byanodic bonding to the deposited etch stop layer 70 which would be firmlybonded to the underlying substrate 36. The term “deposited” as usedherein means a layer formed by a vapor-deposition process from a gas orvapor with or without an involved chemical reaction, or by a sputteringor evaporation process. Next, the spacer plate 50 can be etched asdescribed above in situ, while attached to the substrate 36. The etchingis more easily carried out since the etch stop layer 70 will preventetching of the glass substrate 36 while the etching of the slots 58continues laterally to form the desired steep vertical walls. Also,since the spacer plate 50 is much thinner than the substrate 36 and thusmore fragile, its handling and processing while bonded to the more rigidand stronger substrate 36 is facilitated. In this case, the electrodes30, 31 can be deposited and patterned after the spacer slots 52 areformed. The thin dielectric sheet 45 can then be attached by fritsealing or preferably by anodic bonding to form the assembled channelplate.

In the further variant illustrated in FIG. 7, the etch stop layer 70 isdeposited on the facing surface of the thin dielectric sheet 45. Theunetched spacer plate 50 is then anodically bonded to the etch stoplayer 70 as before, following which the spacer plate 50 is etched asalso described before. The same benefits as are obtained with thevariant described in connection with FIG. 6 are obtained here exceptthat the dielectric sheet 45 is much thinner and thus less rigid thanthe substrate 36. In this case, however, the border region 53 (FIG. 4)can be made wider or thicker to strengthen the spacer plate whenattached to the thin dielectric sheet 45.

In both variants, the etch stop layer 70 can instead be deposited on theunetched spacer plate which is then bonded to the substrate 36 or thethin dielectric sheet 45 as the case may be so that the etch stop layeris positioned between the substrate or thin dielectric sheet and thespacer plate.

As a further alternative, crossbars 62 can be added to the spacer plateas described in the fourth referenced related application to strengthenthe etched spacer plate.

FIG. 8 illustrates still a further variant which enables omitting of thethin dielectric sheet 45 as a separate element. In this modification, acontinuous etch stop dielectric layer 72 is deposited as shown on theouter surface of the unetched spacer plate 50. This etch stop layer canbe made much thicker, for example, 50 μm thick, i.e., thick enough to besufficiently self-supporting to span the subsequently etched slots 52without breaking or being otherwise damaged. Alternatively, a thin etchstop layer 72 can be used as before but with additional continuouslayers 74 deposited on top to increase its strength. As one example, theetch stop 72 can be, for example, of silicon nitride or amorphoussilicon, with a thicker deposited dielectric top layer 74, for example,of spin-on glass or low-temperature deposited silicon dioxide. Asbefore, the slots 52 are then etched in the spacer plate 50, the etchstop layer 72 serving to prevent etching of the materials of the singleor multi-layer deposit 74 above. The completed etched spacer plate 50,with the continuous layers 72, 74 serving now as the thin dielectricsheet to seal off the tops of the channels 20, can be attached to thesubstrate 36. In this case, anodic bonding or glass frit bonding can beused. In this modification, a separate top sheet 45 is unnecessary.

In this last variant, it may be desirable to limit the etching of theslots 58 to the active region to be used as the display area of thecompleted device, so that the frit sealing for sealing the electrodeswhere they exit the discharge space does not come into contact with thethin deposited layers 72, 74 which seal off the top of the channels 20.Moreover, if anodic bonding is used, it may be desirable to etch theregion of the substrate where the electrodes exit the discharge space sothat the electrodes extend below the surface of the substrate as theyexit the discharge space. With this arrangement, the glass frit seal inthe region where the electrodes exit the discharge space will not comeinto contact with the deposited dielectric layers 72, 74, but only withrelatively robust glass sheets.

The broken lines at the edges of the elements in the figures indicatethat what is shown is a small section broken off from a larger assembly,since, as will be appreciated, typically a PALC display device formonitor use would contain several hundred column electrodes 18 andseveral hundred plasma channels 20.

It will be noted that the arrangement described in the fourth referencedrelated application, where the spacer wall portions 58 rest on theelectrically conductive layers 30, 31, which thus remain exposed andable to perform their function of igniting an electrically conductiveplasma when suitable voltages are applied between them, the adjacentchannels thereby sharing a common electrode, can be used in theembodiment described in connection with FIG. 8 in place of separateelectrode pairs for each channel.

The electrode materials are typically of a metal such as copper, orlayers of Cu—Cr—Cu, or other suitable metals.

In a variation of the invention, where the width of the channels 20 maybe large, or where the thin spacer plate 50 acts as the substrate forthe deposited layers 72, 74, it may be desirable to increase themechanical strength of the spacer plate 50. This can be done asillustrated in FIG. 8 by etching strengthening crossbars 62 in thespacer plate 50. The crossbars 62 which extend laterally to and betweenthe spacer walls 58 are thus integral with the plate 60. To avoid thecrossbars 62 from possibly detrimentally affecting the operation of theplasma discharge in the channels 20, their height can be reduced withoutreducing the height of the spacer walls 58. By appropriate masking andetching techniques, easily determined by those skilled in this art, thecrossbars can be made so that they do not extend all the way to theheight of the channels 20.

All of the methods described in the referenced patents and publicationwill be suitable for making the remaining parts of the panel of theinvention.

The invention is generally applicable to all kinds of flat displays, andin particular to displays of the plasma-addressed type, especially PALCdisplays that typically have a small channel pitch for use in computermonitors, workstations or TV applications. While the main application ofthe channel plate of the invention is in PALC type display devices, thesame plasma plate construction 52 can also be used as a plasma displaydevice where the output is the light, generated by the plasma, which canexit the device via the transparent substrate and/or the overlyingtransparent sheet-like member.

Several preferred examples for the FIG. 3 embodiment are (all values arein μm): a wall width of about 20-50; a wall height of about 50-160; anda wall pitch of about 200-500.

It will be appreciated that the drawing figures are not to scale and inparticular the channel widths have been exaggerated to show theelectrodes.

Still further, while the channels in the substrate are typicallystraight, the invention is not limited to such a configuration and otherchannel shapes, such as a meandering shape, are also possible within thescope of the invention.

While the invention has been described in connection with preferredembodiments, it will be understood that modifications thereof within theprinciples outlined above will be evident to those skilled in the artand thus the invention is not limited to the preferred embodiments butis intended to encompass such modifications.

What is claimed is:
 1. A channel plate structure for a flat display,said channel plate structure comprising a dielectric substrate,essentially parallel, spaced flanking wall portions directly contactinga surface of the substrate and positioned, with said surface of thesubstrate to define elongated channels therebetween, a pair of spacedelectrode surfaces provided in each of the channels and a thindielectric sheet-like member provided atop the flanking wall portions,characterized in that: a) the flanking wall portions are parts of anintegral dielectric sheet, b) the surface of the substrate directlycontacted by the flanking wall portions is an ion-containing surface. 2.A channel plate structure as claimed in claim 1, wherein the thindielectric sheet-like member, the dielectric sheet, and the substrateare constituted of glass.
 3. A channel plate structure as claimed inclaim 1, wherein the flanking wall portions are joined at theirperiphery by an integral border region.
 4. A channel plate structure asclaimed in claim 1, wherein the flanking wall portions are laterallyspaced apart by etched slots.
 5. A plasma channel plate structure foruse in a PALC display device comprising elongated channels, each channelprovided with a pair of spaced electrodes and filled with aplasma-containing atmosphere, on an ion-containing surface of asubstantially transparent dielectric substrate, characterized in that:a) on the ion-containing surface is a plurality of deposited spacedelectrically conductive electrode layer portions, b) each of thechannels is defined by a pair of, essentially parallel, spaced wallportions directly contacting areas of the ion-containing surface free ofthe electrode layer portions, said wall portions being part of a spacerplate mounted over the ion-containing surface, and a portion of theion-containing surface provided with a pair of the electrode layerportions and within the pair of wall portions.